Not applicable.
The present invention relates to ink jet printing and in particular discloses a Pump Action Refill Ink Jet Printer.
The present invention further relates to the field of drop on demand ink jet printing.
Many different types of printing have been invented, a large number of which are presently in use. The known forms of print have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.
In recent years, the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles has become increasingly popular primarily due to its inexpensive and versatile nature.
Many different techniques on ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, xe2x80x9cNon-Impact Printing: Introduction and Historical Perspectivexe2x80x9d, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).
Ink Jet printers themselves come in many different types. The utilisation of a continuous stream ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.
U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including the step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilised by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al)
Piezo-electric ink jet printers are also one form of commonly utilized ink jet printing device. Piezo-electric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilises a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode of operation of a piezo electric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) discloses a bend mode of piezo-electric operation, Howkins in U.S. Pat. No. 4,459,601 discloses a Piezo electric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4584590 which discloses a sheer mode type of piezo-electric transducer element.
Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclosed ink jet printing techniques rely upon the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Printing devices utilizing the electro-thermal actuator are manufactured by manufacturers such as Canon and Hewlett Packard.
As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high speed operation, safe and continuous long term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction operation, durability and consumables.
It is an object of the present invention to provide an alternative form of ink jet printing based around ink jet nozzles which utilize a pump action so as to rapidly refill a nozzle chamber for ejection of subsequent ink drops.
In accordance with a first aspect of the present invention, there is provided an inkjet nozzle chamber having an ink ejection port in one wall of the chamber and an ink supply source interconnected to the chamber. The inkjet nozzle chamber can comprise two actuators the first actuator for ejecting ink from the ink ejection port and a second actuator for pumping ink into the chamber from the ink supply source after the first actuator has caused the ejection of ink from the nozzle chamber. The actuators can utilize thermal bending caused by a conductive heater element encased within a material having a high coefficient of thermal expansion whereby the actuators operate by means of electrical heating by the heater elements. The heater elements can be of serpentine form and concertinaed upon heating so as to allow substantially unhindered expansion of said actuation material during heating. The first actuator is arranged substantially opposite the ink ejection port and both actuators form segments of the nozzle chamber wall opposite the ink ejection port and between the nozzle chamber and the ink supply source. The method for driving the actuators for the ejection of ink from the ink ejection port comprises utilizing the first actuator to eject ink from the ejection port and utilizing the second actuator to pump ink towards the ink ejection port so as to rapidly refill the nozzle chamber around the area of the ink ejection port. The method for driving the actuators can comprise the following steps:
(a) activating the first actuator to eject ink from the ink ejection port;
(b) deactivating the first actuator so as to cause a portion of the ejected ink to break off from a main body of ink within the nozzle chamber;
(c) activation of the second actuator to pump ink towards the ink ejection port so as to rapidly refill the nozzle chamber around the area of the ink ejection port;
(d) activating the first actuator to eject ink from the ink ejection port while simultaneously deactivating the second actuator so as to return to its quiescent position; or otherwise
(e) deactivating the second actuator to return to its quiescent position.
The material of the two actuators having a high coefficient of thermal expansion can comprise substantially polytetrafluoroethylene and the surface of the actuators are treated to make them hydrophilic. Preferably, the heater material embedded in the thermal actuators comprises substantially copper. Further, the actuators are formed by utilization of a sacrificial material layer which is etched away to release the actuators. The inkjet nozzle chamber can be formed from crystallographic etching of a silicon substrate. Further, the thermal actuators are attached to a substrate at one end and the heating of the actuators is primarily near the attached end of the devices. The inkjet nozzle is preferably constructed via fabrication from a silicon wafer utilizing semiconductor fabrication techniques.